Human body vibration has been shown to improve health, appearance, fitness, circulation and hormone secretion in humans of all ages. To withstand mechanical energy transferred to the body by vibration, muscles vigorously expand and contract. After repeated sessions of vibration, the body can adjust to the movement, resulting in an increase in muscle performance. Studies have shown that fast, vertical sinusoidal motion can lead to better fitness results when the body undergoes rapid and repeated gravitational force changes and naturally resists these changes.
Conventional body vibration machines are typically made up of a single motor rotating an eccentric weight around a shaft. In these systems, the movement force of the eccentric weight is imparted to the motor as a whole, and can function as a discrete area massager if placed below a flexible surface, such as a cloth, and held against a muscle to be massaged. This massaging action, however, generally imparts very little force on the body, and the body's natural resistance to the vibration felt by it is minimal. Such a massager is shown in U.S. Pat. No. 5,188,096.
Other conventional systems mount a single motor to a fairly rigid platform on which a person may sit or stand. The motor imparts the circular force onto the rigid platform, causing the person to resist the rotating forces of the eccentric weight. A second eccentric weight can also be added to an opposite side of the motor's shaft, imparting alternating diagonal forces on the platform. An example of such a machine is shown in U.S. Pat. No. 2,902,993. However, because much of the force from the eccentric weights in these machines is transferred to the platform, and the person, in a horizontal direction, additional strain can be imparted to the joints of the person, and less vertical force is imparted to the platform for increasing the gravitational forces experienced by the user.